Motor control system for coiling mechanisms



June 2, 1936.

D. I. BOHN MOTOR CONTROL SYSTEM" FOR COILING MECHANISMS Filed May 51,1932 INVENTOR ing mechanism and to regulate-the tension as- PatentedJune 2, 1936 MOTOR CONTROL SYSTEM FOR COILING MECHANISMS Donald I. Bohn,Pittsburgh, Pa., assignor to Aluminum Company of America,.Pittsburgl1,Pa., a corporation of Pennsylvania Application May 31, 1932, Serial No.614,600 n Claims. (oi. 242-75) This invention relates in general tomaterial coiling mechanisms used in conjunction with sheet-processingand/or feeding mechanisms, such as rolling mills or the like, and inparticular to electrical control systems for coiling mechanisms capableof producing constant tension on material delivered from a rolling mill.

In the operation of rolling mills, wherein the material rolled iscoilediupon' a rewind block or drum, the quality of the. materialproduced is materially improved whenla predetermined constant tension isexerted on the material being coiled. To satisfactorily accomplish sucha result it is essential to allow for the increasing diameter of therewind coil, and in the present forms of apparatus, slip gears or clutchmechanisms areused to adjust the torque of the coilthe coil increasesindiameter. Mechanical means of this nature, however, have not provedvery satisfactory because of their low degree of accuracy and because oflost motion and sluggish operation resulting from wear of the variousmechanical parts. For this and other reasons electrically controlledsystems have for the most part replaced these earlier forms ofmechanical devices.

The electricallycontrolled systems which have supplanted theabove-mentioned mechanical de- Vices operate on a common fundamentalprinciple in that the motor driving the rewind drum or coiler and themain mill motor are coordinated, by means of the rewind motor armaturereceiving its voltage from a suitable generator driven by the main millmotor, to produce the required constant tension. In arrangements such asthese the voltage impressed on the rewind motor armature isapproximately proportional at all times to the speed of the mill motorand, assuming the excitation of the rewind motor. field-magnet windingis adjusted to maintain constant current through the armature circuit,such an arrangement insures an approximate constant power input to therewind or coiler motor. Such arrangements, however, offer numerousdisadvantages in that losses in the rewind motor, particularly when therolling mill is slowed down from normal operating speed, introduceerrors in the tension exerted by the rewind or coiling mechanism andwhen the rolling mill is eventually stopped, the tension is entirelyremoved from the material unless auxiliary electrical equipment isemployed to provide a separate source of power in the rewind motorcircuit.

Furthermore, if such a system is provided with auxiliary equipment,which usually takes the form of relays and electrically operatedcontactors in the rewind motor circuit adapted to function as the mainmill motor slows down, the resultant interruption in the current flowcauses fluctu- ,5 ations in the values of torque applied to the coiler,which action produces uneven tension in the ,material being processed.

mill is slowed down to and including zero mill speed. i

A further object of my invention is to provide an electrical controlsystem by means of which a constant tension is maintained on thematerial discharged from the rolling mill in such a manner that therewind motor automatically takes up and maintains any desired presettension on the material being rolled.

This and various other objects, as well as other novel features andadvantages of the invention, will be more apparent when the followingdetailed description is considered in conjunction with the accompanyingdrawing in which:

Fig. '1 represents, in diagrammatic form, my improved arrangement ofconstant tension coiling mechanism; v

Fig. 2 represents an illustration of a particular portion of theapparatus shown in Fig. 1.

Referring to. the drawing, the invention is illustrated as applied tothe control of a rewind or coiling mechanism employed in combinationwith a rolling mill.

The apparatus shown in the drawing comprises a rolling mill, althoughanysuitable feeding mechanism, or the like, can quite manifestly besubstituted therefor, represented'as a pair of working rolls Ill and ii,to which suitable driving means, such as a compound-wound motor i2, iscoupled in any well known manner. The material or stock l3 torbeprocessed is passed between the rolls l0 and ii in the usual fashion andis engaged on the discharge side of the rolling mill upon a coiler orrewind drum l4 of any suitable construction. The coiler is likewiseprovided with a suitable driving motor I5, a shunt-wound, fullycompensated motor being considered preferable.

In accordance with this invention, provision is made for automaticalycontrolling the operation of motor I5 in response to variations in thediameter of the reel I4, whereby the power output of the motor I5 is atall times proportional to the speed of the main mill motor I2 for anydesired preset value of tension on the material I3 being processed.

In accomplishing this result separately excited pilot generators I6 andll of relatively small size are direct-connected to the motors I2 and I5respectively. Generator I6 is equipped with a separately excitedfield-magnet winding I8, adjustable by means of a rheostat I9, whereasgenerator I! is equipped with a field-magnet winding 20 the excitationcontrol of which will be hereinafter described. These generators aresimilar in all respects as to their electrical characteristics and whendriven at the same speed, with equal field excitation, generateequivalent voltages. As will be seen from the drawing, the pilotgenerators I6 and H are electrically connected, in opposed relationship,by means of theconductors 2|, 22 and 23. The coil 24 of a suitable relayin the form of a polarized, contactmaking, zero-center voltmeter 25completes, the circuit between the conductors 22 and 23. The voltmeter25 may be of any suitable construction and is herein shown as comprisinga circuit controlling bridging member 26, a permanent magnet 21, theaforementioned coil 24, and contact members 26 and 29. In operation thebridging member 26 remains midway between the contact members 26 and 29when the voltages generated by the pilot generators I6 and I] are equaland opposite. Any difference in the voltages generated by the pilotgenerators I6 and I1 energizes the coil 24, at which time the bridgingmember 26 is attracted by the permanent magnet 21 into contact witheither one or the other 01. the contact members 26 and 29.

Completion of the circuit through the medium of bridging member 26 andeither of the contactors 28 and 29 serves to connect a reversible,split-field, series motor 30 across the conductors L1 and L2. This isaccomplished by means of the conductors 3|, 32 and 33 throughfield-magnet winding 34; or 3|, 35 and 33 through fieldmagnet winding 36in accordance with the particular'direction in which the bridging member26 is rotated. The field -magnet windings 34 and 36 of motor 30 areoppositely wound and reverse the direction of rotation of this motor.The motor 30 is direct-connected to rheostats A and B, which aresuitably designed in accordance with the characteristics of thefield-magnet windings 31 and 20 of motor I5 and generator II,respectively, the purpose of which willbe hereinafter described. Bymeans of the conductors 38, 39 and 4D rheostat A is connected across thefield-magnet winding 20 of pilot generator II from the main leads L1 andL2. Similarly, by means of conductors 4|, 42 and 43, field-magnetwinding 31 of motor I5 is connected across the leads L1 and L2.

A suitable three-phase synchronous motor 44 i is direct-connected to twogenerators, 45 and 46,

motor I5. The generator 46 and the various elements included in aloop-circuit formed by this generator and the armature of motor I5 areprovided for the purpose of applying a constant armature current to themotor I5 in accordance with any desired preset value of tension upon thematerial being processed.

Also a circuit comprising a suitable current regulator, which forpurposes of illustration has been shown as a compressible carbon pileregulator 5|, is connected in series with the fieldmagnet winding 41 ofthe generator 46, the purpose of which is to control the magnitude ofthe constant current through the armature of motor I5 for any givensetting of the rheostat 55. Conductors 4B, 49 and 52 complete the fieldcircuit of generator 46 with busbars L1 and L2, an adjustable rheostatbeing provided for adjustably controlling the excitation of field-magnetwinding 41. The loop-circuit comprising generator 46 and motor I5 iscompleted through the medium of conductors 53 and 54, and a suitableshunt R of constant predetermined resistance is inserted in theconductor 54. Shunted around the shunt R is a circuit comprising therheostat 55 and an electromagnet coil 56 which cooperates with thecompressible pile regulator 5| in a manner to be described.

In the operation of the electrical control system above described,material or stock having been introduced between the rolls I 0 and II ofthe rolling mill, the mill is set in operation by 'means of any suitablestarter mechanism 66 across the leads 6| and 62 to the mill motor I2.The three-phase synchronous motor 44 directconnected to the D. C.generators 45 and 46 is also set in motion, which action energizes there- 1 wind system. The motor 44 is equipped with any suitableseparately'excited field-magnet winding 63, this excitation being shownas supplied from the conductors L1 and La. Likewise, generator 45 isequipped with field-magnet winding 64 and rheostat 65, conductors 66 and61 being provided to conduct the generated power into the busbars L1 andL2.

To obtain a desired torque on the rewind reel I4 the current applied tothe armature of motor I5 is maintained constant for the particulartorque desired. This is accomplished by means of the circuit comprisingthe rheostat 55 and the electromagnet coil 56 in combination with thecompressible pile regulator 5| in the fieldmagnet winding 41 ofgenerator 46'.

For example, when the motor I5 is operating at zero speed the voltagegenerated by generator 46 is just sufllcient to provide a current in thearmature circuit of motor I5 as determined by the setting of therheostat 55. As the mill motor I2 accelerates motor I5 also acceleratesand during this period the carbon pile regulator functions to increasethe excitation of field-magnet winding 41 of generator 46 to maintain acon-' stant current through the annature of motor I5. This constantcurrent is maintained by regulator 5| as determined by the initialsetting of rheostat 55 and the electromagnet coil 56, the amount ofcurrent through this circuit being inversely proportional to theresistance of this circuit with respect to the resistance of the shuntR. The additional current through the rheostat 55 energizes the coil 56and attracts the core 51 which, through the medium of the pivoted bar58, relieves the pressure on the compressible pile regulator 5| againstthe tension of spring 59. This action permits the discs of the regulator5| to separate and thereby increases the resistance of the field'circuitof the generator 46.

It will be readily seen that as the motor l5 slows down because of theincreased diameter of the coil l4, generator i1 will also slow down andwill generate a lower voltage than generator l6.

4 This differentiation in the voltages generated by is strengthened asits speed decreases.

It will thus be seen that, byproperly designing rheostats A and B, andby maintaining a constant current through the armature of motor I5, thepower output of motor l5 will be constant for a given mill speed. Theseconditions will result in a constant tension on the material beingprocessed regardless of the mill speed down to and including a fullstop. The behavior of rheostat B is the same as though it 'weremechanically operated, as shown diagrammatically in Fig. 2,

wherein a roller 68, supported upon a fulcrumed.

arm 69, rides in contact with the reel lid and through the medium of asuitable link I0 actuates the rheostat B, the contactor arm of which isshown in the form of a bell crank, to cut out resistance in thefiled-magnet winding 3'! as the reel diameter increases. That is,rheostats A and B have definite positions for every outside diameter ofthe material on reel M.

It will be seen that the electrical control system incorporated in thisinvention does not include auxiliary equipment in the armature cir cultof the rewind motor which has heretofore caused intermittent currentsupply resulting in fluctuations in the torque attendant withpreviouslyemployed. electrical control systems.

Having thus described and explained my invention and its mode ofoperation, it is to be understood that the apparatus described wasselected merely for purposes of illustration and that numerousvariations in the form and arra'ngement of parts shown and describedherein may be made without departing from the nature and scope of myinvention except as defined in the appended claims.

I claim:

1. In an apparatus for processing strip material, a feeding mechanism;means for driving said feeding mechanism, a coiler mechanism, anelectric motor for driving said coiler mechanism, a generator driven bysaid feeding mechanism driving means and electrically connected inopposed relationship with a similar generator driven by the coilermechanism electric motor, said similar generators when generatingdifferent voltages being adapted to control the excitation of the coilermotor field-magnet winding, an electrical means incorporated in thecoiler motor armature circuit, whereby a constant torque is developed bysaid coiler motor. 1

2. In an apparatus for processing strip material, a feedingmechanism,means for driving said feeding mechanism, a coiler mechanism,an electric motor for driving said coiler mechanism, a generator drivenby said feeding mechanism driving means and electrically connected inopposed relationship with a similar generator driven by said coilermechanism electric motor, a reversible 7,

driving means, a controllingemeans for said reversible driving means,said controlling means being positioned in the electrical connectionbetween the similar generators and adapted to operate the reversibledriving means when the similar generators generate different voltages,said reversible driving means being adapted to control the excitation ofthe coiler motor fieldmagnet winding, and electrical means incorporatedin said coiler motor armature circuit to maintain constant currenttherein.

3. An apparatus for processing strip material comprising a feedingmechanism and a coiler mechanism, means for driving the feedingmechanism, an electric motor for driving the coiler mechanism, saidelectric motor having a fieldmagnet winding'and an armature circuit,means operated by different-iations in the speed of the feedingmechanism. and the speed of the coiler mechanism to control theexcitation of the fieldmagnet winding, and means in the armature cir-'cult comprising a generator adapted to provide a constant current to-said coiler motor armature.

4. In an apparatus for processing strip mate-' rial, a feeding mechanismand means for driving the same, a coiler mechanism and an electric motorfor driving the same, electrically-operated means for controlling thestrength of the electric motor field, electrically-operated means formaintaining a constant current in the armature n of the electric motor,both of said electricallyoperated means being adapted to maintain thepower output of the coiler mechanism proportional to the speed of thefeeding mechanism.

5. In an apparatus for processing strip material, a feeding mechanismand means for driving the same, a coiler mechanism and an electric motorfor driving the same, similar generators driven by said feedingmechanism driving means and said coiler motor, said similar gen- 6. Inan apparatus for processing strip mate- 0 rial, a feeding mechanism,means for driving said feeding mechanism, a coiler mechanism, anelectric motor for driving said coiler mechanism, a

generator driven by said feeding mechanism driving means andelectrically connected in opposed relationship with a similar generatordriven by the coiler mechanism electric motor, said similar generators,when generating diiferent voltages, being adapted to control theexcitation of the coiler motor field-magnet winding, and adjustablemeans in said coiler motor armature circuit to maintain any presetconstant current therein.

'7. In an apparatus for processing strip material, a feeding mechanism,means for driving said feeding mechanism, a coiler mechanism, anelectric motor for driving said coiler mechanism, a generator driven bysaid feeding mechanism driving means andelectrically connected inopposed relationship with a similar generator driven by said coilermechanism electric motor, a reversible driving means, a controllingmeans for said reversible driving means, said controlling means beingpositioned in electrical connection between the similar generators andadapted to operate the reversible driving means when the similargenerators generate difiere'nt voltages, said reversible driving meansbeing adapted to control the excitation of the coiler motor fieldmagnetwinding, and adjustable electrical means incorporated in said coilermotor armature circuit adapted to maintain constant current therein.

8. In an apparatus for processing strip material, a coilermechanism-adapted to coil the strip material, said coiler mechanismbeing driven by an electric motor, means for exciting the electric motorfiled-magnet winding in response to a differentiation between speeds ofthe processing apparatus and coiler, and an armature circuit for saidelectric motor, including adjustable electrical means for providingconstant current thereto to ;maintain uniform torque.

9. In an apparatus for processing strip material, a feeding mechanism,means for driving said feeding mechanism, a coiler and an electric motorfor driving the same, two similar generators one of which is driven bythe feeding mechanism and the other of which is driven by the coilermotor, said similar generators being connected in opposed relationshipand adapted to generate equal voltages for all difierentiations in speedbetween the feeding mechanism and the coiler, an armature circuit forsaid coiler motor including a generator connected in loop-circuittherewith, and a resistance'having a circuit shunted around the same insaid loop-circuit, said last-mentioned circuit comprising a .rheostatand a current regulator, said loop-circuit being adapted to maintain aconstant current supply .to the armature of the coiler motor for allspeeds thereof.

10. In an apparatus for processing strip material, a reel for receivingand coiling the strip, said reel being driven by an electric motor,means for exciting the electric motor field-magnet winding in responseto a difierentiation between speeds of the processing apparatus andreel, and a loopcircuit including the motor armature and a generator,said loop-circuit being provided with a carbon pile current regulatorfor controllingv the excitation of the generator to maintainv a constantpreset current through the motor arms/.- ture for all speeds of thereel.

DONALD I. BOHN.

